The rigid metal frame holds the paper pots open inside the nursery flat while you fill the paper chain pots with soil. After the soil and seed has been added the frame can be removed, with the soil holding the paper chain pots open.
If your farm is doing a lot of transplanting you may want more than one frame to allow for batch processing and multiple people to fill flats.
The spreader frame is a REQUIRED component of the paper pot system. You can’t use the paper chain pots without this.